If de Blasio can get 40% in Tuesday's balloting, he will avoid a runoff and advance to the general election against either Joe Lhota or John Catsimatidis, the top candidates in the Republican primary. De Blasio has 39% support from likely Democratic voters in the Quinnipiac poll and 36% in the NBC News 4/WSJ/Marist survey.

The surveys also show Democratic primary voters will probably end the comeback bid of Anthony Weiner, who resigned from Congress in 2011 amid a sexting scandal. Weiner, once a front-runner for mayor, dropped in the polls after he acknowledged he continued to send salacious texts to women even after leaving Congress.

Although he is languishing in single digits in the Quinnipiac and Marist polls, Weiner was confident in an interview with NBC's Today show. He said he's "convinced" he'll be the next mayor of New York City.

It's unclear whether voters will advance former New York governor Eliot Spitzer, who resigned amid a prostitution scandal in 2008, in the city comptroller's race. Manhattan Borough President Scott Stringer leads Spitzer, 50% to 43%, among likely Democratic voters in the Quinnipiac Poll. The Marist survey shows a tighter race, with Spitzer leading Stringer 47% to 45%.

The Democratic nominee will face Republican John Burnett in November's general election for comptroller.